1. Field of the Invention
The present invention generally relates to oscillators, and more particularly, to an oscillator having multiple oscillation units capable of outputting different oscillation frequencies.
2. Description of the Related Art
Oscillators, particularly, voltage-controlled oscillators have been used in mobile communication equipment such as PHS (Personal Handyphone System), wireless LAN (Local Area Network), and transceivers.
There is an oscillator capable of oscillating at selectable different frequencies. For example, Japanese Patent Application Publication No. 2004-64567 discloses an oscillator that oscillates at a selected one of three oscillation frequencies. The oscillators are required to have improved C/N (Carrier to Noise) ratios. Further, the oscillator capable of oscillating at selectable oscillation frequencies is required to have a downsized circuitry.